A micro-channel device, such as a biochip, a lab-on-a-chip, etc. has been used to carry a small volume of a sample such as a DNA sample in one or more channels for processing, which, in one instance, has included thermal cycling the sample. By way of example, DNA sequencing has included replicating DNA fragments by a process called polymerase chain reaction (PCR), which requires rapid and precise thermal cycling of the sample multiple times through a predetermined set of temperatures. Unfortunately, temperature fluctuations from any of the predetermined temperatures of more than a half a degree may degrade replication.
A thermoelectric cooler (TEC), such as a Peltier device, is a thermoelectric heat pump, which transfers heat from one side of the device to the other side of the device, and has been used in connection with DNA sequencing for thermocycling samples. In use, a voltage is applied across the TEC device, which is in thermal communication with the portion of the micro-channel device carrying the DNA fragment for PCR, to create a temperature gradient for transferring heat away from the sample to cool the sample and towards the sample to heat the sample to thermal cycle the sample. The polarity of the applied voltage determines whether the device heats or cools the sample.
For PCR, the temperature of a fragment has been estimated based on a temperature at the periphery of the micro-channel device. This temperature is used to regulate the temperature of the TEC device to thermal cycle the DNA fragment based on the set of predetermined temperatures. Unfortunately, this temperature does not well-reflect the temperature of the sample channels. For example, FIG. 1 shows a temperature 102 at the periphery of the device and temperatures 104, 106, 108 at different channels of the device for three different target temperatures 110, 112, 114. As shown, the temperatures 104-108 do not track well to the temperature 102. As a consequence, replication may be degraded.